Editing Livistona mariae (section)

===Palm Growth Rates and Ages: ===
The author was fortunate in
obtaining a number of accurately dated photographs of certain
areas of the valley taken as early as in 1917. Exact
relocation of many of the source points was made possible by
the cliff backgrounds of most of the photographs and the fact
that the narrow valley is restricted in the number of
photographic vantage points.
Almost all of the individuals present in 1917 (when the
photograph was taken) are now still present. The present
heights of the palms were estimated with a Suunto clinometer.
By using the cliff background as a scale, palm heights at the
time of the earlier photograph were estimated. Distortion due
to angle of viewing and to lens aberration was estimated to
be less than 10%. A mean annual growth rate of 10cm was
estimated for this group of palms.
Palms photographed in 1935 however, have grown
approximately 11.5 m in 38 years, a mean annual growth rate
of 30 cm. Palms in this photograph, which apparently were
absent in the earlier photographs, taken in 1918, are now up
to 12 m high, a minimum mean annual growth rate of 22 cm.
Palms grown from seed in Miami, Florida, on the bank of
a permanent stream, grew to a height of 9 to 18 m in 27 years
- an exceptional growth rate of up to 60 cm per year (Lothian
1959). A palm in the cooler climate of Melbourne Botanic
Gardens is reputed to have grown to only 3.75 m in 30 years,
a growth rate of 12.5 cm per year (Australasian Post, 31 May,
1973).
In its natural habitat, the rate of growth of the palm
appears to be mainly dependent on the water supply. The palms
showing the fastest growth rate are at Palm Bend on the bank
of the Finke River about 6 km east of the Valley. This area
has a greater depth of fertile alluvial soil and a better
water supply than most areas in Palm Valley.
The tallest palms in the valley have reached a height of
25 m. Making allowances for different growth rates at various
ages, 100 to 300 years seems a reasonable estimate of the age
of the oldest individuals of ''Livistona mariae''
.